The present invention relates to a method for preparing feed pellets. The process for the addition of sensitive ingredients during the preparation of pellets is so altered that activity losses are minimized. Specifically, the pellets are treated by mixing a suspension or solution of active ingredients in a fluid phase (for example oil or water) under appropriate conditions with carrier material which has been previously granulated.
Feed is generally prepared by mixing different ingredients which are found to be necessary (active ingredients) with carrier materials essential to obtain the feed in the desired form. The desired form may be a powder, a pellet, a solution or a suspension. The preferred form will depend on the application conditions, the composition and the transport.
A well known problem in feed preparation is the loss of active substance during the pelleting process, especially when extrusion is used. Extensive research results have been published describing the loss of activity of the active ingredients during extrusion cooking.
Lee et al. (AIChE Symposium Series (1978) 172: 192-195) investigated the stability of vitamin A in extrusion cooking processing. The percent of retention of the different tested forms of vitamin A ranged from 50 to 100%. This was reported to be relatively stable when compared with the retention of cantaxanthin which was reported to be in the range of 30 to 35%. Berset (Ind. Aliment. Agric. (1987) 104: 529-533) reports a loss of 18% of cantaxanthin when a commercial preparation was treated. Hencken and Estermann (Aquaculture Ind. Develop. Report (1991) 91: 34-51) report a 25 to 48% loss of activity of synthetic astaxanthin during fish feed preparation using extrusion cooking.
A possible solution to this loss of active substance during granulation is to add the active ingredient in a suitable form like a suspension or solution in a fluid phase subsequent to the granulation step. Mixing of components with a fluid phase can be difficult since active ingredients are not always soluble. Furthermore, the addition after the extrusion step makes it more difficult to obtain a homogenous product.
High concentrations of active ingredients in feed for cattle, poultry or fish in a form which is easy to handle and easy to quantify can be obtained by soaking granulated particles with a suspension or solution containing the desired feed or ingredients thereof. The granulated material contains pores which are filled with the solution or suspension and the loaded pellets can easily be used.
The loading of the pellets is generally performed at atmospheric pressure. The process poses some severe drawbacks:
it is difficult to reproduce the amount of suspension or solution which is absorbed into the pellets, this is especially relevant if the aim is to control the amount of fluid (oil etc.) which is fed to the animal concerned,
the pellets are generally preferentially covered at their surface, which may cause problems (like oxidation) of the active ingredient,
the particles in the suspension may block the pores leading to an inefficient use of the particle pore volume and to the above mentioned surface phenomena.
There is thus a lack of reproducibility in dosage of the active substance and a higher chance to losses of active ingredient as a consequence of insufficient penetration of the active ingredient in the feed granule.
To avoid these problems granulated material with wide pores can be used but this evidently leads to loss of strength of the loaded pellets.
The present invention overcomes the problems described above.
The present invention discloses a method for minimizing the loss of activity of sensitive materials due to the well known extrusion process. The invention discloses that this can be done by addition of the material after the extrusion process. The invention is exemplified by the addition of astaxanthin in oil to feed pellets. The invention thus discloses a method for preparing feed pellets loaded with an active ingredient comprising the addition of active material after the extrusion process. The active ingredient is an enzyme, a vitamin, a pigment or a carotenoid. Preferably, the active ingredient is astaxanthin.
The present invention further provides a method for preparing pellets which are homogenously loaded with active ingredient. The method comprises the addition of a suspension or solution of the active ingredients to pellets under reduced pressure and subsequently increasing the pressure. Preferably, the addition is performed under vacuum.
The present invention also provides feed pellets which have been obtained by this method. Specifically, fish meal pellets soaked with an oil suspension containing astaxanthin are disclosed. Such pellets can be recognized by their high degree of loading which is moreover relatively homogenous. A fish pellet is disclosed which contains more than 81.5 mg astaxanthin per kg dry matter.